Without limiting the scope of the invention, its background is described in connection with the Surface Plasmon Resonance ("SPR") phenomenon in connection with miniaturized optical sensors. It should be understood that the principles disclosed may be applied to various sensor configurations including light transmissive, fluorescence-based and critical angle among others.
Optical sensor systems have been developed and used in the fields of chemical, biochemical, biological or biomedical analysis, process control, pollution detection and control and other areas. With SPR-based optical sensors, a resonance is observed when a polarized beam of monochromatic light is totally internally reflected from a dielectric surface having a thin metal film formed thereon. The light internally reflected at the surface has a minimum intensity at a particular angle referred to as the resonant angle. This angle is determined by the dielectric conditions adjacent the metal film and the properties of the film itself. The interface between the sensor surface and the sample of interest shall be referred to as the "sensor/sample interface."
Recent advances in light emitting components and detectors units have allowed the design of small, lightweight, fully integrated sensors. Such sensors can measure less than a few centimeters in length and are easily transported and used near the sample of interest. In addition, since most of the sensor components are readily available their overall cost of manufacturing is low.
While miniaturized sensors are becoming available for use in a wide range of field applications, their effectiveness as an analytical tool is largely determined by the properties of the sample analyte of interest. Fluctuations in sample concentration, temperature and other environmental conditions effect the reactive properties of film deposit in the presence of the sample. Ideally, a controlled amount of the sample with uniform properties is brought in contact with the sensor/sample interface during the sampling process. With larger systems, a flow cell may be used to control the flow rate of the sample. However, there is no equivalent control mechanism for the miniaturized optical sensors.
Accordingly, a device configuration that channels a uniform quantity of the sample analyte of interest across the reactive film deposit of sensor's sampling surface would ensure a more confident analysis.